Reciprocating sander

Abstract

A reciprocating sander particularly adapted for sanding remote surfaces such as ceilings and walls is provided by concentrating a substantial part of the weight of the sander in a motor assembly. A lightweight extension tube extends from the motor assembly to a universal joint which in turn is coupled to a sanding attachment. The sanding attachment includes clips which secures a piece of sandpaper in an mechanism for converting angular rotation of the universal joint into relative reciprocating motion of a sanding plate and sandpaper with respect to the sanding attachment. By bringing relative force between the sanding attachment and the motor assembly, a resiliently retained driving rod within the extension tube, which is coupled to the universal joint and sanding attachment, is forced downwardly in the extension tube toward the motor assembly. This ultimately causes two clutch parts to engage thereby permitting the transmission of the motive force to the sanding attachment. The reciprocating sanding plate carrying the sandpaper has a distance of reciprocation just equal to the overhang of the basal plate of the sanding attachment so that no dead zone is established around the periphery of the sanding attachment which is not effectively reached by reciprocating sandpaper. The universal joint coupling the sanding attachment to the extension tube is provided with contoured mated bearing surfaces so that the universal joint smoothly operates even when the joint is configured into extreme angular configurations which brings opposing parts of the joint in contact with each other.

I claim: 
     
       1. A sanding tool comprising: a lightweight sanding attachment;   a lightweight extension drive tube coupled to said sanding attachment; and   a motor coupled to said extension drive tube, said motor characterized by comprising a substantial portion of the weight of said tool and for providing motive force to said sanding attachment through said extension drive tube,   wherein said sanding attachment is a reciprocating sander,   further comprising a universal joint, said universal joint coupling said extension drive tube and said sanding attachment,   wherein said universal joint is further comprised of a first and second member, said first member coupled to said extension drive tube and said second member coupled to said sanding attachment, said first and second member coupled to each other and rotatable with respect to each other, said first and second member further characterized by a plurality of mating surfaces wherein a predetermined extreme angular orientation of said first member with respect to said second member, said first and second member come into contact and said surfaces of said first and second member form a smooth bearing surface with respect to each other, and wherein said predetermined extreme angular orientations of said first member relative to second member said angular orientation is permitted without interfering with the smooth relative rotation of said first member relative to said second member   whereby a sanding tool is provided for use at positions spaced from said motor by at least a distance equal to the length of said extension drive tube and wherein a substantial portion of the weight of said sanding tool is concentrated in said motor assembly.   
     
     
       2. The tool of claim 1 wherein said sanding attachment comprises a sanding plate and a basal plate, said sanding plate being reciprocatingly driven with respect to said basal plate, said sanding plate characterized by an effective sanding surface, said effective sanding surface of said sanding plate being reciprocatingly disposed during reciprocation to be congruent at least at one point in time with the projection of said basal plate upon said sanding plate. 
     
     
       3. The tool of claim 1, wherein said extension drive tube comprises a resiliently biased rotatable drive rod disposed therethrough and a resiliently biased clutch coupled between said rod and said motor assembly, said resiliently biased clutch being resiliently biased in a disengaged configuration, said drive rod being urged against the resilient bias to cause said clutch to assume an engaged configuration, said drive rod being urged against said resilient bias by pressure being manually applied between said sanding attachment on the one hand and said extension drive tube and motor assembly on the other. 
     
     
       4. A sanding tool comprising: a lightweight sanding attachment;   a lightweight extension drive tube coupled to said sanding attachment; and   a motor coupled to said extension drive tube, said motor characterized by comprising a substantial portion of the weight of said tool and for providing motive force to said sanding attachment through said exension drive tube,   wherein said sanding attachment is a reciprocating sander,   wherein said sanding attachment comprises a sanding plate and a basal plate, said sanding plate being reciprocatingly driven with respect to said basal plate, said sanding plate characterized by an effective sanding surface, said effective sanding surface of said sanding plate being reciprocatingly disposed during reciprocation to be congruent at least at one point in time with the projection of said basal plate upon said sanding plate,   whereby dead areas are substantially eliminated and whereby a sanding tool is provided for use at positions spaced from said motor by at least a distance equal to the length of said extension drive tube and wherein a substantial portion of the weight of said sanding tool is concentrated in said motor assembly.   
     
     
       5. The tool of claim 4, wherein said extension drive tube comprises a resiliently biased rotatable drive rod disposed therethrough and a resiliently biased clutch coupled between said rod and said motor assembly, said resiliently biased clutch being resiliently biased in a disengaged configuration, said drive rod being urged against the resilient bias to cause said clutch to assume an engaged configuration, said drive rod being urged against said resilient bias by pressure being manually applied between said sanding attachment on the one hand and said extension drive tube and motor assembly on the other. 
     
     
       6. A sanding tool comprising: a lightweight sanding attachment;   a lightweight extension drive tube coupled to said sanding attachment; and   a motor assembly coupled to said extension drive tube, said motor characterized by comprising a substantial portion of the weight of said tool and for providing motive force to said sanding attachment through said extension drive tube,   wherein said extension drive tube comprises a resiliently biased rotatable drive rod disposed therethrough and a resiliently biased clutch coupled between said rod and said motor assembly, said resiliently biased clutch being resiliently biased in a disengaged configuration, said drive rod being urged against the resilient bias to cause said clutch to assume an engaged configuration, said drive rod being urged against said resilient bias by pressure being manually applied between said sanding attachment on the one hand and said extension drive tube and motor assembly on the other   whereby a sanding tool is provided for use at positions spaced from said motor by at least a distance equal to the length of said extension drive tube resilient bias by pressure being manually applied between said sanding attachment on the one hand and said extension drive tube and motor assembly on the other.   
     
     
       7. A reciprocating sanding tool comprising: a motor assembly for providing a motive force;   an extension drive tube rigidly coupled to said motor assembly;   an extension drive rod resiliently disposed within said drive tube, said drive rod resiliently urged to assume a preferred longitudinal position while being freely rotatable within said drive tube;   a clutch assembly coupled between said motor assembly and extension drive rod, said clutch resiliently urged into a disengaged configuration;   a universal joint coupled to said drive rod, said universal joint characterized by exterior smooth mating bearing surfaces to permit free sliding contact between the opposing surfaces of said universal joint during operation even when said universal joint is configured into extreme angular configurations;   a basal plate coupled to said universal joint;   a sanding plate coupled to said basal plate, coupling of said sanding plate and basal plate permitting relative reciprocating motion between said sanding plate and basal plate, reciprocation of said sanding plate disposing said sanding plate in space to the same extent as said basal plate extends in space; and   means for converting rotary motion of said universal joint into relative reciprocating motion between said basal plate and sanding plate.   
     
     
       8. The tool of claim 7, wherein said extension drive tube, extension drive rod, universal joint, basal plate, sanding plate and means for converting are each lightweight elements, the substantial portion of weight of said tool being confined to said motor assembly. 
     
     
       9. The tool of claim 7, wherein said extension drive rod is resiliently disposed within said extension drive tube and coupled to said clutch assembly so that the relative force between said sanding plate and said motor assembly coupled through said extension drive tube, universal joint and basal plate causes said clutch assembly to assume an engaged configuration, whereby said motive force is then transmitted from said motor assembly to said sanding plate.   
     
     
       10. The tool of claim 7, further comprising retainer clips disposed at the opposing ends of said sanding plate and gripping bars disposed in said sanding plate opposing each retainer clip, one gripping bar opposing each retainer clip at the set of opposing ends of said sanding plate, said retainer clip being extensible to allow disposition of a sandpaper strip between said retainer clip and gripping bar, said retainer clip being closable against said gripping bar to seize said sandpaper therebetween and lockable in said closed configuration. 
     
     
       11. The tool of claim 10, wherein said retainer clip comprises a pair of resiliently biased locking pins and a housing in which said locking pins are slidingly and telescopically disposed, said locking pins being resiliently urged into a locked configuration within said housing wherein said clip is mechanically temporarily fixed with respect to said sanding plate, said locking pins being selectively disposable within said housing leaving said retainer clip displaced with respect to said sanding plate.